STRUCTURES IMPLICATED IN METAMORPHOSIS. 21 
ment, and observing that the lower part of the head has four 
pairs of attached organs—the upper lip, the mandibles, the jaws, 
and the lower lip—the early separation of the head into four 
segments is fairly inferred: Probably there were six. 
There is an evident design in the manifold differences of the 
jaws and eating apparatus of insects, and the long tubular sucker 
of the butterfly refers to it quite as much as the horny crushing 
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CHRYSALIDES, 
Magnified to show the wing-cases and the rudimentary antenne and other organs. 
(After Réaumur. ) 
a. Wings. 6. Antenne. ¢. Proboscis. 
jaws of many hard-skinned beetles. The change from the leaf- 
cutting jaws of the caterpillar to the suction tube of the butterfly 
is a proof of this unity of plan, and that with different instincts, 
habits, and methods of life there arise different modifications of 
structures. The examination of the mouth of an eating or man- 
dibulate insect is very instructive. Take, for instance, one of 
the grasshopper tribe, and examine the different pieces attached 
around the opening down which the food passes into the stomach. 
The mouth is provided with six articulated pieces :—a labrum, 
or the upper lip, two mandibles, two jaws, or maxilla, and an 
